The present invention relates to a device for the closing of the upper lateral flaps of parallelepiped cases having flaps which can be turned over, particularly for very long cases.
Automatic machines are known which are capable of executing in rapid succession the closing of the upper flaps (first the front one, then the rear one and finally the lateral ones) of a cardboard case which advances with the upper flaps erect, so as to prepare the case in a condition suitable for the subsequent application of an adhesive sealing tape along the separation gap between respective free edges of the lateral flaps folded in the closed position.
For the closing of the lateral flaps the above described machines usually employ a device formed by a pair of helical guides, which, upon meeting the erect lateral flaps, cause their progressive rotation towards the closed position.
In particular, machines are known which, according to the Italian patent application No. 19788 A/85 dated Mar. 6, 1985 in the name of the same inventor (and which corresponds to U.S. Pat. No. 4,698,950, issued Oct. 13, 1987), employ helical guides each formed by two integral and longitudinally staggered portions of a helix, which, one more external and the other more internal, are built upon oblique inlet extremities having horizontal outlet extremities, so that they are engageable by the erect lateral flaps of cases of greater and lesser width , repectively, to execute, in both instances the correct turning over of the flaps in the closed position.
In such a way the device can execute the closing of the lateral flaps of cases having variable width without it being required that the distance between the helices be adjusted each time. The more external portion provided helix to the initial engagement with the lateral flaps of the wider cases, and the more internal portion provide helix to the initial engagement with the lateral flaps of the narrower cases.
Even with this arrangement their remains, however, with no solution the problem of very long cases, whose lateral flaps may enter into engagement with the closing helices, and thus start their closing movement, before the closing device of the rear flap, located upstream from the helices at a fixed distance from them, has been able to act so as to cause the closing of the rear flap. In such an instance as will be understood, the case will not be closed properly.